The invention disclosed herein relates to a method for filling bottles and the like and to a device for implementing the method.
The word "bottles" is used herein as a general designation for bottles, cans and other types of containers as well.
As is well known, counterpressure bottle filling machines comprise a closed annular storage tank which contains the liquid for filling the bottles and has a space for pressurized gas such as carbon dioxide or nitrogen above the liquid. Filler valves extend into the tank. As soon as a bottle becomes coupled to a filler valve, either before or without evacuation of the bottle, the bottle is filled with gas from the tank to assure that all air is displaced from the bottle. The liquid valve is then opened and the gas contained in the bottle is usually returned to the tank through the same tube in the filler valve through which the gas was admitted to the bottle in the first place. Because in the counterpressure filling method the gas pressure in the bottle and in the tank are equalized when filling begins, the liquid flows into the bottle solely under the influence of gravity and foaming is inhibited.
Filler valves usually insert some liquid in the bottle which is in excess of the level to which the bottle should be filled. It is a well-known practice to expel the excess liquid by use of a pressurized gas charge which occurs after the liquid and pressurized gas filling valves have been closed. While the bottle is still coupled to the filler valve a fill level correction valve is opened for the purpose of allowing the pressurized gas in the bottle to expand correspondingly and force the excess liquid that lies above the lower tip of the gas feed and return tube into an annular channel which is below atmospheric pressure.
A merit of this system is that no special source of compressed gas is required for correcting fill level and the counterpressure filling machine can be designed in a simple manner. A disadvantage of this known method, however, is that the quantity of liquid which can be expelled from the bottle is dependent on the volume and the pressure of the pressurized gas in the storage tank. This limits applicability of this method considerably. Thus, for example in practice, when bottles are filled all the way up to their rims under low counterpressure and the liquid being filled is one that foams intensely or when the container shapes are inconvenient to work with, satisfactory filling level correction is impossible.
In another well-known counterpressure filling method a low pressure that is slightly above atmospheric pressure is maintained in a separate region. After the bottle is filled, the gas return tube of the filler valve is connected to the lower pressure region so that the expansion of the gas enclosed in the bottle and in the passageways of the filling unit expel the excess liquid. The disadvantage of this system is that only a very small quantity of excess liquid can be expelled.
In another known type of counterpressure filling machine the bottles are connected with the atmosphere by means of the gas return tube and a throttle valve during the entire filling procedure. After filling of the liquid is complete and while the pressurized gas valve and the liquid feed valve are closed, inert gas under high pressure from a separate container is injected into the bottle for expelling the excess liquid. A good correction in the fill level does not take place in this case since the valve through which the liquid is admitted to the bottle is controlled by an electrical probe in such a way that the level of the liquid cannot rise to the tip of the gas return tube. This known procedure operates with a continuous loss of pressurized gas as well as with the additional use of an inert gas, thus making it a very uneconomical method. In addition, the equipment costs are high because of the additional compressed gas container and the electrical controls which are required.
In still another method for filling bottles under counterpressure conditions where the filler valve has a filling tube, there is a separate pressurized gas and gas return channel and a rotary slide valve for controlling the filling operation. After the liquid flows into the bottle, the rotary slide valve is again brought into the same position which it had while the bottle was being prepressurized before filling it with liquid. In this method, the bottle is connected to a gas chamber in the container for the liquid which is to be filled by means of a pressurized gas line and gas return line while the filling tube is coupled to the atmosphere by way of a relief channel. If a shut-off valve is now opened in the relief channel, then, under the influence of the high pressure resulting from the pressurized gas, the liquid in the gas return line empties into the bottle and the liquid as well as the entire contents of the filling tube are ejected into the atmosphere. This process results in enormous losses of liquid and is no longer used for economic reasons. In addition, the filling machine for practicing this method has a very complicated structure and is difficult to clean.